Biaxially oriented multi-layered bottles may be manufactured from plastic materials such as, for example, polyethylene terephthalate (PET) using a hot preform process, wherein a multi-layered perform is heated to its desired orientation temperature and drawn and blown into conformity with a surrounding mold cavity. The multi-layered preform may be prepared by any conventional process such as, for example, by coinjecting a preform comprising multiple layers of plastic or by injecting subsequent layers of plastic over a previously injection molded preform, known as overmolding. Generally, multiple layers are used for food or carbonated beverage containers, to improve the oxygen or carbon dioxide diffusion barrier properties of the overall package.
The various layers of plastics in the prior art multi-layered containers are generally in intimate contact with one another, thereby facilitating the conduction of thermal energy through the walls of the containers. This allows heat energy to be readily transmitted through the container walls to quickly warm to the contents to ambient temperature. Accordingly, such containers may be sheathed in, for example, a foamed polystyrene shell to impart thermal insulating properties to the container.
It would be desirable to prepare a multi-layered container having foamed walls and improved thermal insulating properties.